Shail K Sharma
Articles written in Journal of Biosciences
Volume 9 Issue 3-4 December 1985 pp 145-157
Studies on the thermal inactivation of adenylate cyclase from neuroblastoma x glioma hybrid cells have been carried out. Inactivation curves show marked deviation from first-order kinetics, and as a first approximation can be adequately described as a sum of two negative exponentials. Half-lives of the rapidly decaying component have been estimated to be 5, 3.4,1.2 and 0.5 min at 37, 40, 44 and 48°C, respectively. The corresponding values for the slow-decaying component are found to be 90, 30, 11 and 5 min. Plausible inactivation pathways responsible for multi-exponential decay curves are discussed. Kinetic curves describing fractional loss of stimulatory response of adenylate cyclase to prostaglandin E1 are shifted downwards with reference to basal activity. In contrast, an upward shift is observed for the inhibitory response of the enzyme to etorphine. A quantitative analysis of the inactivation curves for prostaglandin and etorphine-responsiveness has led to definitive predictions regarding the heat-sensitivity of the ‘hypothetical’ temperature-labile component responsible for the observed shifts.
Volume 11 Issue 1-4 March 1987 pp 423-433
With whole U87MG cells used as antigenic stimulant, two clones 1A5G6 and 1D3A3 secreted monoclonal antibodies which gave intense staining in monolayer cultures of the cells as ascertained by indirect immunofluorescence. Antibodies from clone 1A5G6 stained both the cytoplasm and the processes, and that from clone 1D3A3 stained only the cytoplasm and not the processes. 1A5G6 elicited no cross-reactivity towards human fetal and adult brain and lungs, liver, kidney or spleen, mouse neuroblastoma and melanoma, rat C6 glioma, neuroblastoma X glioma hybrid and normal rat kidney cells. It gave 58–60% cross reactivity with the human neuroblastoma and T-cell leukemia cells. The antigenic comPonent has been identified to be a membrane protein of molecular weight 25–30 kilodaltons by immunoblotting. Using C6 glioma cells as antigenic stimulant 19 clones which were positive for C6 glioma cells, but negative for rat liver cells as inferred by indirect immunofluorescence were selected. Antibodies secreted by all these gave positive reaction towards normal rat kidney and fetal rat kidney cells in culture. Distinct identity of these clones were ascertained by discernible staining patterns in indirect immunofluorescence on C6 glioma cells.
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